class_docstr: Teacher that will shift message['labels'][0] into message['text'] for whatever task
  is specified with --wrapper-task.
  
  Because the dialogue history is effectively overwritten by this action, all episodes
  will be flattened into one example each.
docstr: Edit the fields of the action manually.
docstr_tok: ["Edit","the","fields","of","the","action","manually","."]
code: def _edit_action(self, act: Message) -> Message:
      """
      Edit the fields of the action manually.
      """
      if "labels" in act:
          labels = act["labels"]
          if len(labels) != 1:
              raise ValueError(
                  f"{type(self).__name__} can only be used with one label!"
              )
          act.force_set("text", labels[0])
          act.force_set("labels", [""])
      else:
          assert "text" not in act and act["episode_done"] is True
      act.force_set("episode_done", True)  # Clear the dialogue history
      return act
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  import copy
  from abc import ABC
  from parlai.core.agents import create_agent_from_shared
  from parlai.core.message import Message
  from parlai.core.opt import Opt
  from parlai.core.teachers import create_task_agent_from_taskname, FixedDialogTeacher, Teacher
  from parlai.utils.misc import warn_once
label_desc: Use image node_id 2 for calling the LabelToTextTeacher obj's underlying member method code with example usage: obj._edit_action(act) and returns: act